In the digital still camera market which is growing in recent years, needs for small thin cameras having improved portability are increasing. In the circuit elements that perform signal processing, function improvement and size reduction are progressing, for example, by adoption of finer circuit patterns. Further, in the recording media, those having a small size and a large capacity can be obtained at low prices. Nevertheless, in the imaging devices constructed from an imaging optical system and an image sensor such as a CCD (Charge Coupled Device) sensor or a MOS (Metal Oxide Semiconductor) sensor, size reduction, especially thickness reduction, is not yet achieved satisfactorily. Thus, also for the purpose of realizing cameras having improved portability, development of thin imaging devices is desired.
As a configuration for realizing thickness reduction in an imaging device, a compound eye type imaging device is known in which a plurality of minute lens elements are arranged in a plane. A conventional optical system in which a plurality of lens elements are arranged on the optical axis has problems that the length increases in the optical axis direction and hence the volume increases, and that the lens diameter is large and hence the aberration increases. In contrast, in the compound eye type imaging device, the thickness is reduced in the optical axis direction. Further, since the lens diameter of each minute lens element is small, the aberration can be suppressed to be comparatively small.
For example, Japanese Laid-Open Patent Publication No. 2001-61109 discloses an imaging device that forms an image by means of a plurality of minute image formation optical systems. This imaging device includes: a photoelectric conversion section of a single plane; and an imaging unit array in which a plurality of imaging units are arranged. Then, for individual imaging units, the imaging unit array focuses the light beam from a photographic object at different positions on the photoelectric conversion section.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2001-61109